Messages in this thread | | | Date | Sat, 11 Nov 2006 16:27:57 +0100 | From | Ingo Molnar <> | Subject | Re: [patch] genapic: optimize & fix APIC mode setup |
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* Andi Kleen <ak@suse.de> wrote:
> On Saturday 11 November 2006 16:14, Ingo Molnar wrote: > > From: Ingo Molnar <mingo@elte.hu> > > > > this patch fixes a couple of inconsistencies/problems i found while > > reviewing the x86_64 genapic code (when i was chasing mysterious eth0 > > timeouts that would only trigger if CPU_HOTPLUG is enabled): > > > > - AMD systems defaulted to the slower flat-physical mode instead > > of the flat-logical mode. The only restriction on AMD systems > > is that they should not use clustered APIC mode. > > This will open a race on CPU hotunplug unfortunately (common for multi > core suspend)
Note that i386 still defaults to logical flat mode, so whatever hotplug CPU races there are, they need to be fixed! Given how rare CPU hotplug systems are i have no problem with having these races in the kernel for a while until it's fixed.
Also, distro kernels enable CPU_HOTPLUG frequently. It is just ugly beyond recognition to switch the programming of the IRQ hardware on non-hotplug hardware just because a mostly-software feature (hotplug) is enabled ...
if hotplug breaks suspend then fix it, dont hack it around (on one platform) by slowing down the system [and causing other problems] ...
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